227 research outputs found
Design of Signal Generators Using Active Elements Developed in I3T25 CMOS Technology Single IC Package for Illuminance to Frequency Conversion
This paper presents a compact and simple design of adjustable triangular and square wave functional generators employing fundamental cells fabricated on a single integrated circuit (IC) package. Two solutions have electronically tunable repeating frequency. The linear adjustability of repeating frequency was verified in the range between 17 and 264 kHz. The main benefits of the proposed generator are the follows: A simple adjustment of the repeating frequency by DC bias current, Schmitt trigger (threshold voltages) setting by DC driving voltage, and output levels in hundreds of mV when the complementary metal-oxide semiconductor (CMOS) process with limited supply voltage levels is used. These generators are suitable to provide a simple conversion of illuminance to frequency of oscillation that can be employed for illuminance measurement and sensing in the agriculture applications. Experimental measurements proved that the proposed concept is usable for sensing of illuminance in the range from 1 up to 500 lx. The change of illuminance within this range causes driving of bias current between 21 and 52 mu A that adjusts repeating frequency between 70 and 154 kHz with an error up to 10% between the expected and real cases
Index to NASA tech briefs, 1971
The entries are listed by category, subject, author, originating source, source number/Tech Brief number, and Tech Brief number/source number. There are 528 entries
The 30 GHz solid state amplifier for low cost low data rate ground terminals
This report details the development of a 20-W solid state amplifier operating near 30 GHz. The IMPATT amplifier not only met or exceeded all the program objectives, but also possesses the ability to operate in the pulse mode, which was not called for in the original contract requirements. The ability to operate in the pulse mode is essential for TDMA (Time Domain Multiple Access) operation. An output power of 20 W was achieved with a 1-dB instantaneous bandwidth of 260 MHz. The amplifier has also been tested in pulse mode with 50% duty for pulse lengths ranging from 200 ns to 2 micro s with 10 ns rise and fall times and no degradation in output power. This pulse mode operation was made possible by the development of a stable 12-diode power combiner/amplifier and a single-diode pulsed driver whose RF output power was switched on and off by having its bias current modulated via a fast-switching current pulse modulator. Essential to the overall amplifier development was the successful development of state-of-the-art silicon double-drift IMPATT diodes capable of reproducible 2.5 W CW output power with 12% dc-to-RF conversion efficiency. Output powers of as high as 2.75 W has been observed. Both the device and circuit design are amenable to low cost production
Space Communications: Theory and Applications. Volume 3: Information Processing and Advanced Techniques. A Bibliography, 1958 - 1963
Annotated bibliography on information processing and advanced communication techniques - theory and applications of space communication
Biomedical Engineering
Biomedical engineering is currently relatively wide scientific area which has been constantly bringing innovations with an objective to support and improve all areas of medicine such as therapy, diagnostics and rehabilitation. It holds a strong position also in natural and biological sciences. In the terms of application, biomedical engineering is present at almost all technical universities where some of them are targeted for the research and development in this area. The presented book brings chosen outputs and results of research and development tasks, often supported by important world or European framework programs or grant agencies. The knowledge and findings from the area of biomaterials, bioelectronics, bioinformatics, biomedical devices and tools or computer support in the processes of diagnostics and therapy are defined in a way that they bring both basic information to a reader and also specific outputs with a possible further use in research and development
Readout and Control Beyond a Few Qubits: Scaling-up Solid State Quantum Systems
Quantum entanglement and superposition, in addition to revealing interesting physics in their own right, can be harnessed as computational resources in a machine, enabling a range of algorithms for classically intractable problems. In recent years, experiments with small numbers of qubits have been demonstrated in a range of solid-state systems, but this is far from the numbers required to realise a useful quantum computer. In addition to the qubits themselves, quantum operation requires a host of classical electronics for control and readout, and current techniques used in few-qubit systems are not scalable. This thesis presents a series of techniques for control and readout of solid-state qubits, working towards scalability by integrating classical control with the quantum technology. Two techniques for reducing the footprint associated with readout of gallium arsenide spin qubits are demonstrated. Gate electrodes, used to define the quantum dot, are also shown to be sensitive state detectors. These gate-sensors, and the more conventional Quantum Point Contacts, are then multiplexed in the frequency domain, where three-channel qubit readout and ten-channel QPC readout are demonstrated. Two types of superconducting devices are also explored. The loss in superconducting coplanar waveguide resonators is measured, and a suppression of coupling to the parasitic electromagnetic environment is demonstrated. The thesis also details software for the simulation of Josephson-junction based circuits including features beyond what is available in commercial products. Finally, an architecture for managing control of a scalable machine is proposed where classical components are distributed throughout a cryostat and cryogenic switches route control pulses to the appropriate qubits. A simple implementation of the architecture is demonstrated that incorporates a double quantum dot, a gallium arsenide switch matrix, frequency multiplexed readout, and cryogenic classical computation
Surveyor lunar roving vehicle, phase I. Volume III - Preliminary design and system description. Book 2 - Validation of preliminary design, sections 7-13 Final technical report
Systems design validation of Surveyor lunar roving vehicle - navigation, control and display, television, telecommunications, power supply, and thermal contro
NASA Tech Briefs, Fall/Winter 1981
Topics covered: NASA TU Services: Technology Utilization services that can assist you in learning about and applying NASA technology; New Product Ideas: A summary of selected innovations of value to manufacturers for the development of new products; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Life Sciences; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences
Floating-Gate Design and Linearization for Reconfigurable Analog Signal Processing
Analog and mixed-signal integrated circuits have found a place in modern electronics design as a viable alternative to digital pre-processing. With metrics that boast high accuracy and low power consumption, analog pre-processing has opened the door to low-power state-monitoring systems when it is utilized in place of a power-hungry digital signal-processing stage. However, the complicated design process required by analog and mixed-signal systems has been a barrier to broader applications. The implementation of floating-gate transistors has begun to pave the way for a more reasonable approach to analog design. Floating-gate technology has widespread use in the digital domain. Analog and mixed-signal use of floating-gate transistors has only become a rising field of study in recent years. Analog floating gates allow for low-power implementation of mixed-signal systems, such as the field-programmable analog array, while simultaneously opening the door to complex signal-processing techniques. The field-programmable analog array, which leverages floating-gate technologies, is demonstrated as a reliable replacement to signal-processing tasks previously only solved by custom design. Living in an analog world demands the constant use and refinement of analog signal processing for the purpose of interfacing with digital systems. This work offers a comprehensive look at utilizing floating-gate transistors as the core element for analog signal-processing tasks. This work demonstrates the floating gate\u27s merit in large reconfigurable array-driven systems and in smaller-scale implementations, such as linearization techniques for oscillators and analog-to-digital converters. A study on analog floating-gate reliability is complemented with a temperature compensation scheme for implementing these systems in ever-changing, realistic environments
Supply modulated GaN HEMT power amplifiers - From transistor to system
Power amplifiers (PAs) for mobile communication applications are required to fulfil stringent requirements concerning linearity while keeping a high efficiency over a wide power range and bandwidth. To
achieve this, a number of advanced PA topologies have been developed, mostly based on either load modulation, such as Doherty PAs or load modulation balanced PAs, or on supply modulation such
as envelope tracking or envelope elimination and restoration. Supply modulation has an advantage
over other topologies as the power range of high efficiency can be realised over arbitrary bandwidths,
only limited by the bandwidth of the PA. This does, however, come at the cost of a significantly
more complicated voltage supply. Instead of a static supply voltage, the PA needs to be provided
with one which is rapidly changing, requiring a supply modulator capable of powering the PA while
modulating its supply voltage. This thesis investigates a number of challenges in supply modulated
power amplifiers, ranging from the transistor itself to circuit design and system level considerations
and focusses on power levels up to 10 W and frequencies between 1 GHz and 4 GHz.
Transistors, as the centre-piece of a PA, determine how well the PA reacts to a changing supply
voltage. In this work, the traits that make GaN HEMTs suitable for supply modulated PAs were
investigated, and gain variation with changing supply voltage was established as an important parameter. This gain variation is described in detail and its impacts on PA performance are discussed. By
comparing transistors in literature, gain variation has been demonstrated to be a prevalent characteristic in transistors with GaN HEMTs showing a very wide range of gain variation. Using a small-signal
model based on measurements, the voltage dependent behaviour of the feedback capacitance CGD is,
for the first time, identified as the origin of small-signal gain variation. This is traced down to the
gate field plate which is commonly used to combat surface trapping effects in GaN HEMTs. With
this in mind, two different ways of changing the transistor geometry to reduce the impact of gain
variation and thus optimise the transistor for operation in supply modulated PAs are discussed and
demonstrated using a 250 nm GaN HEMT.
As a result of the non-linearity of the feedback and gate-source capacitances, the input impedance
of GaN HEMTs changes with supply voltage and drive power. This prevents the transistor from being
matched at all supply voltages and input powers and introduces phase distortion. Using simulation and
measurement, the impact of input impedance on linearity and efficiency of supply modulated power
amplifiers is demonstrated on a 2.9 GHz 10 W PA. Careful selection of the input impedance allows
improvement of AM/PM distortion of a supply modulated PA with little cost in terms of AM/AM
and PAE.
I
Supply modulators have a significant impact on efficiency and linearity of the ET system. One
supply modulator topology with the potential to generate a supply voltage with a high modulation
bandwidth is the RF modulator in which the input DC voltage is turned into an RF signal and
rectified, resulting in an output voltage which depends on the excitation of the PA. While PAs are
well understood in every detail, there are gaps in the understanding of RF rectifiers. Using active
load-pull/source-pull measurements, intrinsic gate and drain waveforms of a GaN HEMT operated as
a rectifier are demonstrated for the first time. This allows in-detail evaluation of the impact of the
gate termination in self-synchronous rectifiers. It also allows detailed analysis of the loss mechanisms
in rectifiers and formulation of the required impedances to realise efficient self-synchronous operation,
resulting in efficiencies exceeding 90% over wide power ranges. Using waveform engineering, a new type
of RF modulator, with potentially very high bandwidths, based on even harmonic generation/injection
is proposed. The necessary operating conditions of the rectifier part of the modulator are emulated
using an active load-pull/source-pull system to successfully demonstrate that the rectifier behaves
as predicted. Using a simple demonstrator, preliminary measurements were conducted and the RF
modulator was shown to work, reaching efficiencies up to 78%.
As PA and supply modulator are combined, they present impedances to each other. These
impedances have a significant impact on the behaviour of both sub-systems. A simple way to characterise both the impedance presented to the PA by the modulator and the impedance presented to the
modulator by the PA is described. Using a state-of-the-art modulator, these impedances are measured,
the modulator impedance is demonstrated to be close to the simulated value. These measurements
also demonstrate that the impedances change significantly with the operating conditions
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